Prophet Hud - 11:62
"They said: "O Salih, before this you were a popular source of hope among us. Do you now forbid us from what our forefathers used to serve? We are in doubt about what you call us to."
Why does Allah not forgive those who die serving others besides Him?
The Women/4:48
Allah does not forgive associating partners with Him, but other than that He forgives to whom He wills. Whoever associates partners with Allah has committed a great insult.
The Women/4:116
Allah does not forgive associating partners with Him (if it continues until death), but He forgives the sins below that to whom He wills. Whoever associates partners with Allah has gone astray.